Reducing the data communication delay in wireless sensor networks

We study the problem of delay efficient scheduling of data communicated by sensor nodes for sensor fusion in wireless sensor networks. We model the sensor network as a tree in which sensor nodes collaboratively observe an event and transmit their measurements to intermediate sensor nodes that lie along the path the root of the tree. The root node functions as the sensor data fusion center that is responsible for aggregating distributed measurements, while internal tree nodes perform dual functionality - as local routers and as intermediate data fusion nodes. We are interested in two problems - one for minimizing the sum of the end-to-end delays of sensors, and the other for minimizing the maximum end-to-end delay of a sensor. Since these problems are computationally hard, we approach these problems by minimizing the average delay and the maximum delay one hop at a time. We provide low complexity, distributed optimal solutions for both these problems. Further, we show through simulations that by minimizing the delay hop by hop, we can achieve good delay performance relative to the global problem of minimizing the sum of the end-to-end delays.